Discharge power supply apparatus

ABSTRACT

This discharge power supply apparatus is for supplying a D. C. voltage to a discharge load  6  and discharging the same. The discharge power supply apparatus includes an inverter circuit  2  that converts D. C. voltage to A. C. voltage; a transformer  3  having a primary winding  3   a  to which the A. C. voltage output by the inverter circuit  2  is supplied and a secondary winding  3   b ; a full-wave rectifier circuit  4  that has a plurality of diodes  4 A to  4 D and rectifies the A. C. voltage generated by the secondary winding  3   b ; and a trigger capacitor  7  connected in parallel to a part of the diodes of the full-wave rectifier circuit  4.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a discharge power supply apparatus thatsupplies stationary discharge power following a discharge state that hasbeen caused by the application of a trigger voltage to a discharge load.Priority is claimed on Japanese Patent Application No. 2003-273348,filed on Jul. 11, 2003, and on Japanese Patent Application No.2003-273349, filed on Jul. 11, 2003, the contents of which areincorporated herein by reference.

2. Description of Related Art

Various types of laser apparatuses, discharge lamps, strobe lightapparatuses, electric discharge machines, fusion splicers for opticalfibers, thin film formation apparatuses and the like are examples of adischarge loads that use discharge energy. A variety of discharge loadsare used in a wide range of fields. The discharge for this kind of loadis generated in a vacuum, in a special gas such as an inert gas, or inthe atmosphere. To start the discharge, it is necessary to apply atrigger voltage that is higher than the stationary discharge voltagebetween the discharge electrodes of the discharge load. The triggerpower is small in comparison to the discharge power, but when the powersupply apparatus does not have the capacity to supply an adequatetrigger power, the voltage between the discharge electrodes does notrise sufficiently due to leakage between the discharge electrodes duringthe triggering (i.e., during the supply of the trigger voltage forstarting the discharge), and thereby the discharge state is notattained. After the discharge has been generated between the dischargeelectrodes, the discharge is maintained for a time at a voltage that islow in comparison to the trigger voltage, and thereby a power that cancause the flow the necessary discharge current can be supplied.

A conventional discharge power supply apparatus is shown in FIG. 13. InFIG. 13, the input side rectifier circuit 51 converts a three-phasealternating voltage to direct current power by rectification, and theinverter circuit 52 converts the direct current voltage output from theinput side rectifier circuit 51 to a high frequency alternating currentvoltage of several kHz to several 10 kHz. The inverter circuit 52 iswell known, and normally is pulse width controlled (ON time ratiocontrol). The transformer 53 inputs the high frequency alternatingcurrent voltage applied from the inverter circuit 52 at the primarywinding 53 a, raises the alternating current voltage by a predeterminedtransformation ratio, and outputs this alternating current voltage fromthe secondary winding 53 b. The alternating current voltage of thesecondary winding 53 b is converted to a direct current voltage by thefull-wave rectifier circuit 54 on the output side, smoothed by thecapacitor 55, and applied to the discharge load 56. The discharge load56 normally is grounded by one terminal, and a negatively biased voltageis applied to the other terminal.

In the conventional discharge power supply apparatus having such astructure, if the commercial alternating current input voltage is AC200V, the voltage after rectification by the input side rectifiercircuit 51 is approximately 260V. Therefore, if the stationary dischargevoltage of the discharge load 56 is 500V, the winding ratio of thesecondary winding 53 b to the primary winding 53 a in the transformer53, that is, the transformation ratio n, can be approximately 2. Whenthe trigger voltage is 1000V, the transformation ratio n must beapproximately 4 in order to generate this trigger voltage.

In the conventional discharge power supply apparatus, the invertercircuit 52 is controlled at the maximum pulse width at the start of thedischarge, and a trigger voltage of 1000V is generated. The dischargeload 56 is triggered by this 1000V trigger voltage, and after transitionto the stationary discharge state, the voltage between the dischargeelectrodes of the discharge load 56 falls to approximately 500V, whichis the stationary discharge voltage. Thus, the ON time ratio (pulsewidth) of the inverter circuit 52 must be made small.

However, when the ON time ratio of the inverter circuit 52 is madesmall, the peak value of the output current of the inverter circuit 52increases, and because the effective value increases, there are theproblems that the power loss of the switching elements in the invertercircuit 52 becomes large, and the heat of the switching elements and thewinding loss of the transformer 53 increase.

In order to eliminate these drawbacks, the apparatus shown in FIG. 14has been proposed. In this apparatus, the essential elements identicalto those in FIG. 13 are denoted by identical reference numerals, andtheir explanation is omitted. In this conventional apparatus, inaddition to the secondary winding 53 b, a second secondary winding 53 cfor supplying an approximately 500V trigger voltage is providedseparately in the transformer 3. The voltage of this second secondarywinding 53 c is rectified by the trigger rectifier 57, and anapproximately 500V voltage is applied to both terminals of a bypassdiode 59 through the resistor 58. The 500V voltage at both terminals ofthe bypass diode 59 is superimposed on the 500V rectified voltage of thefull-wave rectifier circuit 54, and an approximately 1000V voltage issupplied to the discharge load 56.

In this power supply apparatus, the discharge is started by theapplication of the trigger voltage, the bypass diode 59 becomesconductive after the transition to the stationary voltage, and thesecond secondary winding 53 c is shorted. Thus, a resistor 58 forcontrolling the short-circuit current becomes necessary. During thestationary discharge, the resistor 58 consumes the wasted power, andthis invites both the lowering of the efficiency and heat generation.

As can be understood from the above explanation, the conventionaldischarge power supply apparatus has the drawbacks that the structureand control are complicated, power loss occurs, and the cost is high.

It is an object of the present invention to provide an apparatus, inwhich, using a simple circuit configuration, the control method for theinverter circuit does not become complicated, a large trigger voltagecan be supplied at the start of the discharge, and after the start ofthe stationary discharge, the apparatus can maintain the stationarydischarge state while limiting as much as possible the peak of thecurrent that flows through the inverter circuit.

SUMMARY OF THE INVENTION

The discharge power supply apparatus of the present invention includesan inverter circuit that converts direct current voltage to alternatingcurrent voltage; a full-wave rectifier circuit that has a plurality ofdiodes and rectifies the alternating current voltage generated by theinverter circuit; and a trigger capacitor that is connected in parallelto a portion of the diodes of the full-wave rectifier circuit. In thisapparatus, at the start of the discharge of the discharge load, atrigger voltage that is higher than the stationary output voltage issupplied to the discharge load, and after the start of the stationarydischarge, a direct current output by the full-wave rectifier circuit issupplied to the discharge load.

According to this discharge power supply apparatus, by using a simplecircuit configuration, it is possible to apply a voltage that issubstantially double the stationary discharge voltage to the dischargeload as the trigger voltage. In addition, because the trigger voltage isgenerated each cycle, the discharge dissipates with difficulty even whenthe discharge voltage becomes small due to changes in the operatingconditions.

The full-wave rectifier circuit can be a full-bridge rectifier circuitproviding two pairs of diodes connected serially, and trigger capacitorscan be connected in parallel to either pair of diodes.

In this case, by using a simple circuit configuration, it is possible toobtain a trigger voltage that is substantially double the magnitude ofan arbitrary a stationary discharge voltage, and it can be applied whenthe time necessary for the trigger must be shortened or when a hightrigger voltage is required.

A transformer having a primary winding and a secondary winding to whichthe alternating current voltage output from the inverter circuit issupplied can also be provided.

The transformer can have two secondary windings, and the two secondarywindings can be connected together serially. The full-wave rectifiercircuit can be a center tapped rectifier circuit, this center tappedrectifier circuit can be connected to the two secondary windings, andthe trigger capacitor can be charged up to a voltage equal to the sum ofthe voltages generated by the two windings.

In this case, by using a simple circuit configuration, it is possible toobtain a trigger voltage that is substantially double the stationarydischarge voltage, and the time required for the trigger can be reduced.

In the case that the trigger capacitor is connected in parallel to onediode, if the leakage current flowing through the discharge load isdenoted by It(A), the stationary discharge voltage is denoted by E(V),and the frequency of the alternating current voltage output by theinverter circuit is denoted by F(Hz), then the capacitance C(F) of thetrigger capacitor is C>It/(E×F), and the capacitance C(F) can be equalto or less than the capacitance at which full-wave rectification iscarried out when the discharge load is in the stationary dischargestate.

In this case, the control of the inverter circuit does not becomecomplicated and the discharge load reliably attains the discharge state.At the same time, the power loss of the inverter circuit and thetransformer and the like can be suppressed.

In the case that the trigger capacitor is connected in parallel to twodiodes, if the leakage current flowing through the discharge load isdenoted by It(A), the stationary discharge voltage is denoted by E(V),and the frequency of the alternating current voltage output by theinverter circuit is denoted by F(Hz), then the capacitance C(F) of thetrigger capacitor is C>It/(2×E×F), and the capacitance C(F) can be equalto or less than the capacitance at which full-wave rectification iscarried out when the discharge load is in the stationary dischargestate.

In this case, the control of the inverter circuit does not becomecomplicated, a high trigger voltage can be applied, and the dischargeload reliably attains the discharge state. At the same time, the powerloss of the inverter circuit and the transformer and the like can besuppressed.

Capacitors can be connected in parallel to all the diodes of therectifier circuit, and one of the capacitors among these can be atrigger capacitor having an electrostatic capacitance that issubstantially larger that that of the other capacitors.

A discharge power supply apparatus of another embodiment of the presentinvention includes an inverter circuit that converts direct currentvoltage to alternating current voltage, a full-wave rectifier circuitthat rectifies the alternating current voltage generated by the invertercircuit, a trigger capacitor and a trigger diode connected seriallybetween the input side and the output side of the full-wave rectifiercircuit, and a charging diode connected between the input side of thefull-wave rectifier circuit and the junction between the triggercapacitor and the trigger diode. This apparatus supplies to thedischarge load a trigger voltage that is higher than the stationaryoutput voltage by superimposing the voltage of the trigger capacitoronto the voltage of the secondary winding at the start of the discharge,and supplies to the discharge load direct current power that is outputby the full-wave rectifier circuit after start of the stationarydischarge.

According to this discharge power supply apparatus, by using a simplecircuit configuration, it is possible to apply a voltage that issubstantially double the stationary discharge voltage to the dischargeload as the trigger voltage. Because the trigger voltage is generated ateach cycle, even in the case that the discharge current becomes smalldue to fluctuations in the conditions and the like, the dischargedissipates with difficulty.

At the output of the full-wave rectifier circuit, a smoothing capacitoror a smoothing capacitor and a bypass diode are provided, and thecathode of the trigger diode and the cathode of the bypass diode can beconnected.

In this case, by using a simple circuit configuration, it is possible toobtain a trigger voltage that is substantially double the stationarydischarge voltage, and this can be applied when the time necessary forthe trigger can be shortened or when a high trigger voltage is required.

A transformer that has a primary winding, to which the alternatingcurrent output voltage of the inverter circuit is applied, and asecondary winding, can also be provided.

The transformer can have two secondary windings that are connectedserially, the full-wave rectifier circuit can be a center tappedrectifier circuit consisting of a pair of diodes that are connectedserially to the respective terminals of the two secondary windings, andthe charge diode can be connected between the junction of the twosecondary windings connected serially and the junction between thetrigger capacitor and the trigger diode.

In this case, by using a simple circuit configuration, it is possible toobtain a trigger voltage that is substantially double the stationarydischarge voltage, and the time required for the triggering can bereduced.

The transformer can have an auxiliary winding connected serially to oneend of the secondary winding, and the charging diode can be connectedbetween the other terminal of the auxiliary winding and the junction ofthe trigger capacitor and the trigger diode.

In this case, by using a simple structure, it is possible to obtain atrigger voltage that is substantially double the stationary dischargevoltage, and the time required for the triggering can be shortened.

If the discharge current before the start of the discharge is denoted byIt(A), the discharge voltage in the stationary discharge state isdenoted by E(V), and the conversion frequency of the inverter circuit isdenoted by F(Hz), then the capacitance C(F) of this capacitor may be avalue that satisfies the formula C>It/(F×E).

In this case, without the control of the inverter circuit becomingcomplex, the discharge load can reliably attain the discharge state, andit is possible to suppress the power loss of the inverter circuit,transformer and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing discharge power supply apparatus ofthe first embodiment of the present invention.

FIGS. 2A to 2C are circuit diagrams for explaining the operation of thedischarge power supply apparatus shown in FIG. 1.

FIG. 3 is a graph showing the simulation effect.

FIG. 4 to FIG. 12 are circuit diagrams showing other differingembodiments of the present invention.

FIG. 13 and FIG. 14 are circuit diagrams showing examples of aconventional discharge power supply apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Below, the embodiments of the present invention will be explained withreference to the figures. However, the present invention is not limitedto only these embodiments, and various modifications within the scope ofthe claims are possible. For example, the essential elements in each ofthe embodiments can be interchanged, well known essential elements canbe added, or a portion of the essential elements can be omitted.

FIG. 1 is a circuit diagram showing a first embodiment of the dischargepower supply apparatus of the present invention, and FIGS. 2A to 2C arecircuit diagrams for explaining the operation thereof. The input siderectifier circuit 1 converts a single-phase alternating current voltageto direct current voltage by rectification, and the inverter circuit 2converts this direct current voltage to a high frequency alternatingcurrent voltage of, for example, several kHz to several 10 kHz. Thealternating current input in this example is a single-phase alternatingcurrent, but can be an alternating current having three or more phases.In this case, the rectifier 1 can be a bridge rectifier having three ormore phases. The inverter circuit 2 carries out, for example, pulsewidth control (ON time ratio control). However, the inverter circuit 2can be an inverter circuit that carries out control other than pulsewidth control, such as frequency modulation control or the like.

In the transformer 3, the high frequency alternating current voltagefrom the inverter circuit 2 is applied to the primary winding 3 a, andan alternating current voltage is output from the secondary winding 3 bthat has been stepped up at a predetermined transformation ratio. Inthis example, a transformer is used, but in the case that thealternating current power source and the discharge load 6 do not need tobe isolated from each other, the transformer can be omitted.

The alternating current voltage from the secondary winding 3 b is fullyrectified by the full-wave rectifier circuit 4, which acts as a bridgecircuit by connecting the four diodes 4A to 4D, is then smoothed by thesmoothing capacitor 5, and finally is applied to the discharge load 6.One terminal of the discharge load 6 can be grounded, as shown in thefigure, and between the discharge electrodes (not illustrated), anegatively biased direct current voltage can be applied.

The trigger capacitor 7 is connected in parallel to one diode 4A amongthe four diodes 4A to 4D of the full-wave rectifier circuit 4. Thetrigger capacitor 7 can also be connected in parallel to any among theother diodes 4B, 4C, and 4D, and is not limited to just the diode 4A.

The control circuit 8 receives a voltage detection signal from thevoltage detector 9, which detects the discharge voltage, and the currentdetection signal from the current detector 10, which detects the outputcurrent, and these are multiplied together to calculate the power value.Based on this detected power value, the control circuit 8 carries outpulse width control of the inverter circuit 2 such that the powersupplied to the discharge load 6 attains a predetermined value that hasbeen set in advance. Note that the isolation of the current detectionsignal and the control circuit is unnecessary if the current detector 10carries out detection from the current on the positive electrode side,that is, the ground potential side.

The operation of the embodiment shown in FIG. 1 will be explained. Asshown in FIG. 2A, in the half cycle in which a negative bias is appliedto one terminal A of the secondary winding 3 b and a positive bias isapplied to the other terminal B, the current flows from the terminal Bthrough the diode 4C, the trigger capacitor 7, and the terminal A, andcharges the trigger capacitor 7 up to a voltage E at the illustratedpolarity. During the next half cycle, a positive bias is applied toterminal A and a negative bias is applied to terminal B, and thereby, asshown in FIG. 2B, the voltage E of the trigger capacitor 7 issuperimposed on the alternating current voltage E of the secondarywinding 3 b, and the superimposed voltage 2E is applied between thedischarge electrodes (not illustrated) of the discharge load 6.

As will be explained below, a leakage current flows in an actualdischarge load 6. In each cycle, the operation described above isrepeated, and the trigger capacitor 7 is charged up to the alternatingcurrent voltage E of the secondary winding 3 b. When the triggercapacitor 7 has been charged up to voltage E, the voltage 2E, which isthe superimposition of the voltage E of the trigger capacitor 7 on thealternating current voltage of the secondary winding 3 b, is applied tothe discharge load 6 via the smoothing capacitor 5, and thereby thedischarge of the discharge load 6 is started. During the operation inwhich the smoothing capacitor 5 is charged by the voltage 2E, only thediodes 4C and 4D are conducting, while the diodes 4A and 4B aresubstantially non-conducting. That is, the trigger capacitor 7 and thediodes 4C and 4D function as a irregular half-wave voltage doublerrectifier circuit.

The time period during which the trigger capacitor 7 is being charged upto voltage E is controlled by the capacitance of the trigger capacitor7, and as shown in FIG. 3, the larger the capacitance of the triggercapacitor 7, the more quickly the charge time is completed.

The voltage 2E must have a sufficient voltage value and energy to causea discharge between the discharge electrodes of the discharge load 6,and must be able to trigger the discharge electrodes reliably and makethem attain the plasma discharge state. The gas between the dischargeelectrodes is ionized due to the start of the discharge. The impedancebetween the discharge electrodes is reduced due to the ions producedbetween the discharge electrodes, and thereby the discharge voltage isreduced. Therefore, the process transitions to the next half cycle whilemany ions are present between the discharge electrodes. If there is acapacity that can supply the current necessary for the power source tomaintain the discharge, the stationary discharge can be maintained by avoltage that is small compared to the trigger voltage. When thestationary discharge state has been attained, as shown in FIG. 2C, thevoltage of the discharge load 6 becomes E.

When the capacitance C of the trigger capacitor 7 is too small, it isnot possible to charge the trigger capacitor 7 up to the voltage E dueto the leakage current It flowing though the discharge load 6, and thusit is not possible to start the discharge between the dischargeelectrodes (not illustrated) of the discharge load 6. Next, thenecessary electrostatic capacitance C of the trigger capacitor 7 isfound.

If the leakage current of the discharge load 6 before the start of thedischarge is denoted by It(A) and one cycle of high frequencyalternating current voltage of the secondary winding 3 b of thetransformer 3 is denoted by T (seconds), then the leakage chargequantity Q(C) due to the leakage voltage It during one cycle T isQ=It×T.

When the leakage quantity Q is all discharged as the leakage current It,if the voltage value ΔV(V), which is the reduced charging voltage of thesmoothing capacitor 5, is not smaller than the voltage E(V), then thecharging voltage of the smoothing capacitor 5 cannot be stepped up tovoltage 2E, which is double. Therefore, the formula ΔV=Q/C<E holds, andthis formula becomes:C>Q/E=It×T/E=iT/(E×F),where F is the frequency (Hz) of the high frequency alternating currentvoltage of the secondary winding 3 b of the transformer 3, that is, theconverted frequency of the inverter circuit 2, and is the reciprocal ofthe cycle T.

As can be understood from this formula, when the capacitance C of thetrigger capacitor 7 is smaller than It/(E×F), the trigger capacitor 7does not attain the voltage E because of the influence of the leakagecurrent It. Therefore, the trigger voltage does not rise to 2E, and thusit is difficult to make the discharge load 6 attain the discharge state.The capacitance C of the trigger capacitor 7 must be a value thatsatisfies the formula C>It/(E×F). However, in practice, because thepower loss and the time necessary for the triggering must also be takeninto account, to make the discharge load 6 attain the discharge statereliably and in a short amount of time, the capacitance C of the triggercapacitor 7 is preferably equal to or greater than 1.5 times It(E×F). Ifthe capacitance C of the trigger capacitor 7 is made equal to or greaterthan 1.5 times It(E×F), the charging voltage of the trigger capacitor 7reliably rises for each cycle of the high frequency alternating currentvoltage, and the discharge load 6 is triggered in a short amount oftime. When the discharge load 6 is triggered and the discharge isgenerated at the discharge load 6, the voltage of the discharge load 6falls, and the power is supplied to the discharge load 6 after thefull-wave rectifier circuit 5 carries out a full-wave rectification.

In contrast, if the capacitance C of the trigger capacitor 7 is toohigh, when the discharge load 6 has attained the stationary dischargestate, the time interval during which the power is supplied to thedischarge load 6 through only the trigger capacitor 7, that is, the timeinterval during which the full-wave rectifier circuit 4 carries outhalf-wave voltage doubler rectification, becomes long. When thefull-wave rectifier circuit 4 carries out the half-wave voltage doublerrectification, the output voltage (2E) becomes higher than that of thefull-wave rectification, and thus the inverter circuit 2 shortens thepulse width, and it is operated using a short pulse width. Because thenecessary discharge current flows at this short pulse width, the peakvalue of the current suddenly becomes large, and not only do switchingsemiconductor elements having a large current capacity become necessaryin the inverter circuit 2, but the power loss becomes large. Therefore,preferably the capacitance C of the trigger capacitor 7 takes thenecessary minimum value, where capacitance C is taken into account.

The upper value of the capacitance C is influenced by the loadconditions, for example, the discharge current supplied to the dischargeload 6, the gap between the discharge electrodes (not illustrated) inthe discharge load 6, the degree of the vacuum and the type of gas inthe atmosphere around these discharge electrodes, and thus cannot beunconditionally determined. When the load conditions for the dischargeload 6 have been determined, experimentation is carried out according tothese load conditions. The capacitance C of the trigger capacitor 7 isselected such that during the stationary discharge the full-waverectifier circuit 4 transits from half-wave rectification to a full-waverectification, and the capacitance C at this time becomes the uppervalue.

In this manner, if the capacitance C of the trigger capacitor 7 islarger than It/(E×F), and preferably, 1.5 times larger than It/(E×F),then it is possible to trigger the discharge load 6 reliably. However,although a ripple voltage during stationary discharge becomes largebecause the energy charged to the trigger capacitor 7 moves to thesmoothing capacitor 5 each cycle even after the start of the stationarydischarge, this energy does not become a useless power loss because itis used as discharge energy. Note that the capacitance C of the triggercapacitor 7 is taken into account, and is not limited to this range.Ultimately, the range should be determined by experiment.

Based on the conception described above, design was carried out, and thesimulated results are shown in FIG. 3. The conditions are as follows:

-   (1) the stationary discharge voltage Eo=500V-   (2) the discharge current Io during stationary discharge=20 A (where    the load resistance is 25 Ω)-   (3) the trigger voltage Vt=1000V-   (4) the leakage current It before triggering=10 mA (where the load    resistance is 100 kΩ)-   (5) the effective value Vo of the output voltage of the high    frequency power source=260V-   (6) the transformation ratio n of the transformer=2.

Argon (Ar) gas is used in the atmosphere around the discharge electrodes(not illustrated) of the discharge load 6 to generate a plasmadischarge. In the simulation, the inverter circuit 2 was replaced with ahigh frequency alternating current power source having an effectivevalue of 260V. As the discharge load 6, before triggering the discharge,a 100 kΩ load resistance that simulates the current load is connectedand a leakage current is caused to flow. After start-up, when the loadvoltage reaches 1000V, triggering occurs, and the load resistance isswitched by a switch to a 25 Ω resistance that simulates a plasmadischarge load.

By the above equation, the minimum capacitance C of the triggercapacitor 7 is C=It/(E×F)=0.1/(500×20³)=1 nF, and thus simulations werecarried out for the cases of 0.9 nF, which is a smaller capacity thanthe minimum capacity, 1 nF, which is the minimum capacity, and 1.1 nF,1.2 nF, 1.5 nF, and 3 nF.

The results of these simulations are shown, in order, by the respectivecurves A to F. In the case of the curve A (0.9 nF), the charging voltageof the trigger capacitor 7 does not attain 500V, and thus the necessarytrigger voltage (1000V) is not attained, and the discharge load 6 is nottriggered. In the case of curve B and curve C, although not illustrated,1000V is attained after a long period of time. However, in an actualapparatus, it is difficult to select such capacities.

In the case that the capacity of the trigger capacitor 7 is 1.2 nF(curve D), in a comparatively short time, the trigger voltage rises to1000V, and after start-up, the trigger capacitor 7 is triggered in about110 ms, and transits to the plasma discharge. In the case that thecapacitance C of the trigger capacitor 7 is 1.5 nf (curve E), thetrigger voltage rises to 1000V in an even shorter period of time, thetrigger capacitor 7 is triggered in about 40 ms, and transits to aplasma discharge. In the case that the capacitance C of the triggercapacitor 7 is 3 nF (curve F), the trigger voltage rises to 1000V is aneven shorter period of time, the trigger capacitor 7 is triggered inabout 20 ms, and transits to a plasma discharge. In FIG. 3, the hatchedarea (width), which shows the discharge generation, illustrates theripple voltage of the discharge voltage.

FIG. 4 shows a second embodiment of the present invention. In FIG. 1, afull-bridge rectifier circuit is used as a full-wave rectifier circuit4, whereas in this embodiment, a center tapped rectifier circuit isused. In FIG. 4, elements that are identical to those in FIG. 1 aredenoted by identical reference symbols and their explanation is omitted.

The transformer 3 provides a secondary winding 3 b and a secondarywinding 3 c connected serially. Between the secondary windings 3 b and 3c, a center point 3 d is provided as the center tap. The terminals A andB of the secondary windings 3 b and 3 c are respectively seriallyconnected to the diodes 4A and 4B, and thereby a center tap full-waverectifier circuit 4 is formed. The full-wave rectifier circuit 4 carriesout operations that are identical to the first embodiment.

One diode 4A and the trigger capacitor 7 are connected in parallel.Instead of the diode 4A, the diode 4B and the trigger capacitor 7 can beconnected in parallel. If the voltages generated by the secondarywindings 3 b and 3 c are denoted by E, then when a negative bias isapplied to the terminal A and a positive bias is applied to the terminalB, the trigger capacitor 7 is charged up to at a voltage 2E. Next, whena positive bias is applied to the terminal A and a negative bias isapplied to the terminal B, the voltage E(V) of the secondary winding 3 bis superimposed on the charging voltage 2E of the trigger capacitor 7,the 3E(V) trigger voltage is applied to the discharge load 6 via thesmoothing capacitor 5, and the discharge load is triggered. Therefore,the circuit in this embodiment is applied when a trigger voltage that israther high in comparison to the stationary discharge voltage isnecessary.

FIG. 5 shows a third embodiment of the present invention. In FIG. 1, aportion of the diodes, which are bridge connected to form the full-waverectifier circuit 4, is connected to the trigger capacitor 7. Incontrast, as shown in FIG. 5, in this discharge power supply apparatus,among the two rows of diodes that form the bridge circuit of thefull-wave rectifier circuit 4, the diodes 4A and 4B, connected serially,are respectively connected to the trigger capacitors 7 and 7′. In FIG.5, the elements identical to those in FIG. 1 are denoted by identicalreference symbols, and their explanation is omitted.

The operation of this discharge power supply apparatus will beexplained. During the half-cycle when a positive bias is applied to theterminal B and a negative bias is applied to the terminal A, the highfrequency alternating current voltage E of the secondary winding 3 bcharges the trigger capacitor 7 by passing through the diode 4C from theterminal B. Next, during the half-cycle when a positive bias is appliedto the terminal A and a negative bias is applied to the terminal B, thehigh frequency alternating current voltage E of the secondary winding 3b flows through the trigger capacitor 7′ and the diode 4D, and thetrigger capacitor 7′ is charged. This operation is repeated. When eitherthe trigger capacitor 7 or the trigger capacitor 7′ has been charged upto a voltage equal to the alternating current voltage E of the secondarywinding 3 b, the voltage 2E is applied to the discharge load 6 via thesmoothing capacitor 5, and the discharge load 6 is triggered and attainsthe stationary discharge state.

In this discharge power supply apparatus, only the diodes 4C and 4D areconductive in each cycle before the trigger, and diodes 4A and 4B aresubstantially non-conductive. This means that the trigger capacitors 7and 7′ and the diodes 4C and 4D form the full-wave voltage doublercircuit. Because a voltage doubler operation is carried out at the twotrigger capacitors 7 and 7′, in principle the capacitance C of thesecapacitors can be one-half the capacitance C (C>It/(2×E×F)) of thedischarge power supply apparatus in FIG. 1.

FIG. 6 is another embodiment of the present invention. In thisembodiment, a three-phase rectifier 101 is used as the input rectifier.The output of the three-phase rectifier 101 is supplied to a three-phaseinverter 102, and the output from the three-phase inverter 102 issupplied to the three-phase transformer 103. The output of thethree-phase transformer 103 is supplied to the three-phase full-waverectifier circuit 104 to be full-wave rectified.

The three-phase inverter in this example consists of six MOSFETs 2A to2F. The three-phase transformer 103 consists of the three star connectedprimary windings 3A, 3B, and 3C and three star connected secondarywindings 3D, 3E, and 3F. The three-phase bridge rectifier circuit 104consists of the six diodes 4A to 4F. The three-phase inverter 102produces alternating current voltages that have a 120° phase differenceon the three alternating current output lines a, b, and c. Thealternating current voltages are rectified by the three-phase bridgerectifier circuit 104 after being transformed by the transformer 103. Inthis three-phase method, the ripples in the output direct currentvoltage can be reduced in comparison to the embodiment (single phasemethod) in FIG. 1.

The detailed explanations of the three-phase discharge powertransformation apparatus consisting of the three-phase inverter 102,three-phase transformer 103, and the three-phase bridge rectifiercircuit 104 are omitted. The control circuit 108, the voltage detectingcircuit 109, and the current detecting circuit 110 correspondrespectively to the elements 8, 9, and 10 in the explanation for FIG. 1.

In this embodiment, among the three rows of diodes that form thethree-phase bridge rectifier circuit 104, the trigger capacitors 107Aand 107B are connected to the serially connected diodes 4A and 4B. Byadding the trigger capacitors 107A and 107B, it is possible to generatea voltage that is higher than the stationary voltage before starting thedischarge. Diodes 4C and 4D or 4E and 4F can be connected instead of thediodes 4A and 4B. It is also possible to connect the capacitor to onlyone diode among these six diodes. Moreover, various inductances andcapacitances can be connected serially to the three alternating currentoutput lines a, b, and c of the three-phase inverter 102 to form what iscalled a series resonant inverter, and frequency modulation control canbe carried out.

FIG. 7 shows another embodiment of the present invention. In thisembodiment, all four diodes 4A to 4D are connected in parallel to therespective capacitors 7A to 7D. If all the capacitors 7A to 7D have asubstantially identical capacitance, the capacitors of this circuitconfiguration can suppress surge voltages applied to the diodes 4A to 4Dand reduce the recovery noise in the diodes 4A to 4D.

However, in this embodiment, the output voltage before starting thedischarge can be made higher than the stationary discharge voltage bymaking the electrostatic capacitance of the two capacitors 7A and 7Bthat are connected in parallel to one of the rows consisting of diodes4A and 4B (4C and 4D can also be used) larger than the remainingcapacitors 7C and 7D.

Like the embodiments shown in FIG. 1 and FIG. 5, the voltage generationprinciple of the embodiment in FIG. 7 is voltage doubler rectification.Taking into account the appropriate electrostatic capacitancecorresponding to the leakage current is complicated due to the presenceof the capacitors 7C and 7D, and thus cannot be adequately clarified.However, the difference between the electrostatic capacitance of thecapacitors 7A, 7A′, 7B, and 7B′ and the electrostatic capacitance of thecapacitors 7C, 7C′, 7D, and 7D′ can be selected by the followingformula, which takes into account the electrostatic capacitance C:C=It/(2×E×F)

The reason that the coefficient 2 is entered in the denominator is that,like the conception of the embodiment in FIG. 5, the capacitors 7A and7B parallel to the two diodes 4A and 4B are provided a trigger capacitorfunction. When only the capacitor 7A is made larger than the othercapacitors 7B, 7C, and 7D, like the embodiment in FIG. 1, thisdifference becomes the electrostatic capacitance represented by thefollowing formula:C=It/(E×F)

Concretely, the capacitance of the capacitors is selected underconditions that are identical to the previous simulation conditions. Forexample, if the electrostatic capacitance of the capacitors 7C and 7D is1 nF, preferably the electrostatic capacitance of the capacitors 7A and7B is equal to or greater than 5 nF. A capacitor is connected only tothe one diode D1.

FIG. 8 shows another embodiment of the present invention. In thisembodiment, a total of four diodes of the full-wave rectifier circuit 4are replaced by the serially connected pairs of diodes 4A and 4A′, 4Band 4B′, 4C and 4C′, and 4D and 4D′. The capacitors 7A to 7D′ arerespectively connected in parallel to all the diodes 4A to 4D′.

If the capacitors all have substantially identical electrostaticcapacities, each of the capacitors acts as a capacitor that balances theexcess voltage of the serial diodes. However, in the present invention,the output voltage before the start of the discharge can be made higherthan the rated discharge voltage by making the electrostatic capacitanceof the two capacitors 7A, 7A′, 7B, 7B′ that are connected togetherserially and connected to the diodes 4A and 4A′, and 4B and 4B′ in onlyone serial arm in parallel substantially larger than the remainingcapacitors 7C, 7C′, 7D, and 7D′.

The voltage generating principle of the example in FIG. 8 is the voltagedoubler rectification identical to the embodiments in FIG. 1, FIG. 5,and FIG. 7, but taking into account the appropriate electrostaticcapacitance corresponding to the leakage current is complicated due tothe presence of the capacitors 7C, 7C′, 7D, and 7D′, and thus cannot beadequately clarified. However, the difference between the serialelectrostatic capacitance of the capacitors 7A and 7A′, and the serialelectrostatic capacitance of the capacitors 7B and 7B′, and the serialelectrostatic capacitance of the remaining capacitors 7C and 7C′ and theserial electrostatic capacitance of the capacitors 7D and 7D′ can beselected by the following formula, which takes into account theelectrostatic capacitance C(F):C=It/(2×E×F)

The reason that the coefficient 2 is entered in the denominator is that,like the conception of the embodiment in FIG. 5, two trigger capacitorsare used. When only the capacitors 7A and 7A′ are made larger than theother capacitors 7B, 7B′, 7C, 7C′, 7D, and 7D′, this difference becomesthe electrostatic capacitance C represented by the following formula:C=It/(E×F)

Concretely, the capacitance of the capacitors is selected underconditions that are identical to the previous simulation conditions. Forexample, when the electrostatic capacitance of the capacitors 7C, 7C′,7D, and 7D′ is 2 nF, preferably the electrostatic capacitance of thecapacitors 7A, 7A′, 7B, and 7B′ is equal to or greater than 4 nF. Thecapacitors 7A and 7A′, which have a larger electrostatic capacitancethan the others, can be connected to only the group of diodes 4A and4A′.

In each of the embodiments described above, the smoothing capacitor 5 isconnected in parallel to the discharge load 6, but the smoothingcapacitor 5 can be eliminated in order to make the discharge energyduring an arc discharge small.

In addition, the inverter can be formed by IGBTs or bipolar transistors,not only MOSFETs, and the bridge inverter is not limited.

FIG. 9 shows another embodiment, and the operation thereof is identicalto that explained using FIG. 3. After the three-phase alternatingcurrent voltage is rectified and converted to direct current power bythe input side rectifier circuit 1, the inverter circuit 2 converts thisdirect current voltage to a high frequency alternating current voltageof several kHz to several 10 kHz. The inverter circuit 2 is well known,and for example, and may be pulse width controlled (ON time ratiocontrolled). The transformer 3 inputs at the primary winding 3 a thehigh frequency alternating current voltage output from the invertercircuit 2 applied. This alternating current voltage is stepped up at apredetermined transformation ratio and output from the secondary winding3 b. The alternating current voltage of the secondary winding 3 b isfull-wave rectified by the full-wave rectifier circuit 4, which has fourdiodes connected to a bridge (not illustrated), smoothed by thesmoothing capacitor 5, and applied to the discharge load 6. Thedischarge load 6 normally has one terminal grounded, and a negativelybiased direct current voltage is applied between the dischargeelectrodes (not illustrated). Between the input side of the full-waverectifier circuit 4 (that is, the junction between one of the outputs ofthe full-wave rectifier circuit 4 and the one terminal A of thesecondary winding 3 b of the transformer 3) and the output side of thefull-wave rectifier circuit 4 (that is, the junction between the outputof the full-wave rectifier circuit 4 and the discharge load 6), acircuit in which the trigger capacitor 7 and the trigger diode 8 areconnected serially is connected across the full-wave rectifier circuit4. A charging diode 9 for charging the trigger capacitor 7 is connectedbetween the other output side of the full-wave rectifier circuit 4 (thatis, the junction between the other input of the full-wave rectifiercircuit 4 and the other terminal B of the secondary winding 3 b of thetransformer 3) and the junction of the trigger capacitor 7 and thetrigger diode 8.

The control circuit 10 receives the voltage detection signal and thecurrent detection signal respectively from the voltage detector 11 thatdetects the load voltage and the current detector 12 that detects theoutput current, and carries out pulse control of the inverter circuit 2such that the power supplied to the discharge load 6 becomes apredetermined value.

During the half cycle in which a negatively biased voltage is applied tothe one terminal A of the secondary winding 3 b and a positively biasedvoltage is applied to the other terminal B, the current flows from theterminal B through the charging diode 9, the trigger capacitor 7, andthe terminal A, and charges the trigger capacitor 7 with the illustratedpolarity. During the next half cycle, a positively biased voltage isapplied to the terminal A and a negatively biased voltage is applied tothe terminal B, and thereby the voltage of the trigger capacitor 7 issuperimposed on the alternating current voltage E of the secondarywinding 3 b, and this superimposed voltage is applied between thedischarge electrodes (not illustrated) of the discharge load 6.

As will be described below, because a leakage current It flows in anactual discharge load, the trigger capacitor 7 cannot attain thealternating current voltage E in each cycle, but the trigger capacitor 7is gradually charged up to the alternating current voltage E of thesecondary winding 3 b by repeating the operation as described above ineach cycle. When the trigger capacitor 7 has been charged up to thevoltage E, the voltage 2E, which is the voltage of the trigger capacitor7 superimposed on the alternating current voltage E of the secondarywinding 3 b, is applied to the discharge load 6 after passing throughthe smoothing capacitor 5, and the discharge load 6 is triggered. Thefull-wave rectifier circuit 4 carries out a full-wave rectification tosupply the discharge power.

The time during which the trigger capacitor 7 is charged up to thevoltage E is determined by the size of the capacitance of the triggercapacitor 7, and as shown in FIG. 3, the larger the capacitance of thetrigger capacitor 7, the more quickly the charging time is completed.

The voltage 2E has a sufficient voltage value and energy to cause thedischarge between the discharge electrodes (not illustrated) of thedischarge load 6, and must cause the discharge electrodes to attain thedischarge state reliably. Due to the starting of this discharge, the gasbetween the discharge electrodes is ionized, the impendence between thedischarge electrodes is reduced, and this discharge voltage becomessmall. Therefore, the process proceeds to the next cycle while many ionsare present between the discharge electrodes, and if there is a capacityin which the voltage necessary for the power source to maintain thedischarge can be supplied, the stationary discharge can be maintained ata voltage that is small compared to the trigger voltage.

When the capacitance C of the trigger capacitor 7 is too small, it isnot possible to charge the trigger capacitor 7 up to the voltage E dueto the leakage voltage It flowing through the discharge load 6, and thusit is not possible to start the discharge between the dischargeelectrodes (not illustrated) of the discharge load 6. Next, in order togenerate the voltage 2E, which is double the winding voltage, theminimum necessary capacitance C of the trigger capacitor 7 must befound.

If the leakage current of the discharge load 6 before starting thedischarge denoted It and one cycle of the high frequency alternatingcurrent voltage of the secondary winding 3 b of the transformer 3 isdenoted T, then the leakage charge quantity Q due to the leakage currentIt in one cycle T is Q=It×T.

If the charge quantity Q has all been discharged as leakage current It,when the voltage value ΔV, which is the reduced charging voltage of thesmoothing capacitor 5, is not smaller than the voltage E, the chargingvoltage of the smoothing capacitor 5 cannot rise to the voltage 2E,which is double. Therefore, the formula ΔV=Q/C<E holds, and this formulabecomes C>Q/E=It×T/E=It/(E×F), where F denotes the frequency of the highfrequency alternating current voltage of the secondary winding 3 b ofthe transformer 3, that is, the conversion frequency of the invertercircuit 2, and is the reciprocal of the cycle T.

taken into consideration, and therefore, to make the discharge load 6attain the discharge state reliably and in a short time, the capacitanceC of the trigger capacitor 7 is preferably 1.5 times or greater thanIt/(E×F). The charging voltage of the trigger capacitor 7 will reliablyrise during each cycle of the high frequency alternating current voltagedue to selecting a value that is 1.5 times or greater than It/(E×F), andthe discharge load 6 can be triggered in a short period of time.

In contrast, when the capacitance C of the trigger capacitor 7 is toolarge, the discharge load 6 attains the stationary discharge state andthe full-wave rectifier circuit 4 carries out the full-waverectification. When the power is supplied to the discharge load 6, thepower is supplied to the discharge load 6 via only the trigger capacitor7. This means that a time period occurs during which the full-waverectifier circuit 4 is carrying out a half-wave rectification. When thefull-wave rectifier circuit 4 carries out a half-wave rectification,naturally the conduction period becomes short, and thus the invertercircuit 2 limits the pulse width, and operates at a short pulse width.Because the necessary discharge current flows at a short pulse width,the peak value of the current becomes high, and not only does aswitching semiconductor element having a large current capacity becomenecessary in the inverter circuit 2, but the power loss becomes large.Therefore, the capacitance C of the trigger capacitor 7 is preferablysmaller than the maximum capacitance Cu at which the diodes 4A to 4D ofthe full-wave rectifier circuit 4 are not cut off, that is, thefull-wave rectifier circuit does not transit from a full-waverectification to a half-wave rectification.

The maximum capacitance of the trigger capacitor 7 is influenced by theload conditions, for example, the discharge current supplied to thedischarge load 6, the gap between the discharge electrodes (notillustrated) in the discharge load 6, the degree of the vacuum and thetype of gas in the atmosphere around these discharge electrodes, and thelike, and therefore cannot be determined unconditionally. Experimentsthat depend on the load conditions are carried out, and the capacitanceC of the trigger capacitor 7 at the time that the full-wave rectifiercircuit 4 transits from full-wave rectification to half-waverectification is made the maximum capacitance.

In this manner, in the case that the capacitance C of the triggercapacitor 7 is larger than It/(E×F), preferably 1.5 times larger, and atthe same time smaller than the maximum capacitance Cu, the dischargeload 6 can be reliably triggered. Although the discharge load 6 can bereliably triggered, after the start of the stationary discharge theenergy that has charged the trigger capacitor 7 moves to the smoothingcapacitor 5 in each cycle, and thus the ripple voltage during stationarydischarge becomes large. However, this energy is used as dischargeenergy, and thus does not constitute useless energy loss.

Design is carried out based on the concept described above, and theresults of simulation are as shown in FIG. 3. The conditions are asfollows:

-   (1) the stationary discharge voltage Eo=500V-   (2) the discharge current Io during stationary discharge=20 A (with    a load resistance of 25 Ω)-   (3) the trigger voltage Vt=1000V-   (4) the leakage voltage It before triggering=10 mA (with a load    resistance of 100 kΩ)-   (5) the effective value Vo of the output voltage of the high    frequency power source=260V-   (6) the transformation ratio n of the transformer 3=2

A plasma discharge is generated using argon (Ar) gas in the atmospherearound the discharge electrodes (not illustrated) in the discharge load6. In the simulation, the inverter circuit 2 was replaced by a highfrequency alternating current power source having an effective value of260V. As the discharge load 6, before triggering the discharge, a 100 kΩload resistance that simulates the current load is connected and aleakage current is caused to flow. After start-up, when the load voltagereaches 1000V, triggering occurs, and the load resistance is switched bya switch to a 25 Ω resistance that simulates a plasma discharge load.

According to the following formula, the minimum capacitance C of thetrigger capacitor 7 is:C=It/(E×F)=0.01/(500×20³)=1 nFThus a simulation was carried out for the cases of 0.9 nF, where thecapacitance is smaller than the minimum capacitance; 1.0 nF, in whichthe minimum capacitance; a slightly larger 1.1 nF; and further for 1.2nF, 1.5 nF, and 3 nF.

The results of the simulation are respectively shown in the sequence ofcurves A to F. In the case of curve A (0.9 nF), the charging voltage ofthe trigger capacitor 7 does not attain 500V, the necessary triggervoltage (1000V) is not attained, and thus the discharge load 6 is nottriggered. In the case of curve B (1.0 nF) and curve C (1.1 nF),although not illustrated, a long time is required to attain 1000V.However, because the time up to discharge is too long, in an actualapparatus, selection of this type of voltage is difficult.

In the case that the capacitance of the trigger capacitor 7 is 1.2 nF(curve D), the trigger voltage rises up to a voltage of 1000V in acomparatively short time, triggering occurs in about 10 ms, and there isa transition to a plasma discharge. It can be understood that when thecapacitance C of the trigger capacitor 7 is 1.5 nF (curve E), thetrigger voltage rises up to 1000V in an even shorter time, triggeringoccurs in about 40 nm, and there is a transition to a plasma discharge.In the case that the capacitance C of the trigger capacitor 7 is 3 nF(curve F), it can be understood that the trigger voltage rises up to1000V in an even shorter time, triggering occurs in about 20 ms, andthere is a transition to a plasma discharge. Although not illustrated, acapacitance C of the trigger capacitor 7 up to 2000 nF was simulated,and the plasma discharge was generated in an even shorter required time.

FIG. 10 shows a discharge power supply apparatus of another embodiment.In FIG. 10, the reference symbols that are identical to those used inFIG. 9 denote names of the elements that are identical to the elementsin FIG. 9.

This embodiment differs from the discharge power supply apparatus shownin FIG. 9 on the point that a bypass diode 13 is serially connectedbetween the smoothing capacitor 5 and the discharge load 6, and at thesame time, the cathode of the bypass trigger 13 is connected to thecathode of the trigger diode 8.

By providing a bypass diode 13 in this manner, the trigger voltage 2E isnot smoothed by the smoothing capacitor 5, and the trigger voltage 2E isdirectly applied to the discharge load 6. Thereby, the discharge load 6is triggered quickly. When the discharge load 6 is triggered and adischarge state is attained, the discharge power is supplied to thedischarge load 6 from the secondary winding 3 b of the transformer 3through the full-wave rectifier circuit 4, the smoothing capacitor 5,and the bypass diode 13. According to this embodiment, the readiness isimproved.

In addition, the output voltage of the full-wave rectifier circuit 4 isblocked by the trigger voltage 2E due to the bypass diode 13, and onlythe voltage E is applied. Thus, there is the advantage that thebreakdown voltage of the diodes that form the full-wave rectifiercircuit 4 and the breakdown voltage of the smoothing capacitors 5 can beone-half in comparison to the discharge power supply apparatus 100 inFIG. 9.

FIG. 11 shows a discharge power supply apparatus of another embodiment.In FIG. 11, the reference symbols identical to those in FIG. 9 denoteparts having names identical to those in FIG. 9.

In the transformer 3, a secondary winding 3 c is added serially to thesecondary winding 3 b, and the secondary windings 3 b and 3 c have acenter tap structure having the center 3 d. The anodes of the diodes 4Aand 4B are respectively connected serially to the terminals A and B ofthe secondary winding 3 c that has been added to the secondary winding 3b, and the cathodes are connected together to form the center tapfull-wave rectifier circuit 4.

The circuit in which the trigger capacitor 7 and the trigger diode 8 areconnected serially is connected between the terminal A of the secondarywinding 3 b and the cathodes of the diodes 4A and 4B. The charging diode9 for charging the trigger capacitor 7 is connected between the junctionof the trigger capacitor 7 and the trigger diode 8, and the center point3 d. The operation of this discharge power supply apparatus issubstantially identical to the operation of the discharge power supplyapparatus es 100 and 200, and the explanation thereof is omitted.

FIG. 12 shows yet another embodiment. In FIG. 12, the reference symbolsidentical to those in FIG. 9 denote parts having names identical tothose in FIG. 9. This embodiment differs from the discharge power supplyapparatus shown in FIG. 9 on the point that the anode of the chargingdiode 8 is connected to terminal B of the added secondary winding 3 c.

The operation of the discharge power supply apparatus 400 will beexplained. During the cycle in which a negative bias is applied to theterminal A of the secondary winding 3 b and a positive bias is appliedto the terminal B of the added secondary winding 3 c, voltage 2E, whichis the superimposition of the voltage E of the secondary winding 3 b andthe voltage E of the added secondary winding 3 c, is applied to thetrigger capacitor 7 through the charging diode 9, and the triggercapacitor 7 is charged up to voltage 2E. Therefore, according to thedischarge power supply apparatus 400, as can be understood from theprevious explanation, the voltage 3E is applied to the discharge load 6.

According to this embodiment, if the trigger voltage of the dischargeload 6 is the voltage 2E, when the trigger capacitor 7 is charged to thevoltage E, the voltage 2E is applied to the discharge load 6, and it istriggered. Thus, it is possible to start the discharge of the dischargeload 6 in a short time. In addition, the trigger voltage can be appliedup to 3E. Furthermore, in this embodiment, if the number of windings ofthe secondary winding 3 c is increased in comparison to the number ofwindings of the secondary winding 3 b to correspond to the necessaryvoltage, this embodiment can be applied to a discharge load having atrigger voltage that is higher than 3E.

The smoothing capacitor 5 connected in parallel to the discharge load 6is for decreasing the discharge energy when the discharge load 6 is inan arc discharge state, and can be omitted.

The uses of the present invention are, for example, a power source fortriggering a laser tube in a laser apparatus such as an excimer laser;an electrical light apparatus for igniting various types of electricallight such as a high intensity discharge (HID) lighting; a dischargepower supply apparatus for optical fiber fusion connection wherein, whenthe cross-sectional faces of optical fibers are abutted in order to beconnected, the optical fibers are fused by heat generated by adischarge; and a thin film formation apparatus in which a plasma gas isionized by generating a plasma discharge, these ions bombard the targetsurface, the target material is vaporized, and the vapor thereof forms athin film on a semiconductor surface of an optical disk substratesurface. In addition, it can be used as a discharge power source forvarious devices that use discharge energy between electrodes.

According to the present invention, by using a simple circuitconfiguration and the simple normal control methods for an invertercircuit, it is possible to generate reliably a discharge in a dischargeload and maintain the stationary discharge state.

1. A discharge power supply apparatus for supplying a direct currentvoltage to a discharge load and discharging the same, comprising: aninverter circuit that converts direct current voltage to alternatingcurrent voltage; a full-wave rectifier circuit that has a plurality ofdiodes and rectifies an alternating current voltage generated by saidinverter circuit; and a trigger capacitor connected in parallel to aportion of said diodes of said full-wave rectifier circuit, wherein, atthe start of the discharge of said discharge load, a trigger voltagethat is higher than a stationary output voltage is supplied to thedischarge load, and after the start of the stationary discharge, thedirect current voltage output by said full-wave rectifier circuit issupplied to said discharge load.
 2. A discharge power supply apparatusaccording to claim 1, wherein said full-wave rectifier circuit is afull-bridge rectifier circuit including two serially connected pairs ofdiodes, and the trigger capacitor is connected in parallel to any one ofthe pairs of said diodes.
 3. A discharge power supply apparatusaccording to claim 1, further comprising a transformer having a primarywinding, to which the alternating current voltage output by saidinverter circuit is supplied, and a secondary winding.
 4. A dischargepower supply apparatus according to claim 3, wherein said transformerhas two of said secondary windings, said two secondary windings areconnected together serially, said full-wave rectifier circuit is acenter tap rectifier circuit, said center tap rectifier circuit isconnected to said two secondary windings, and said trigger capacitorsare charged up to a voltage equal to the sum of the voltages generatedby said two secondary windings.
 5. A discharge power supply apparatusaccording to claim 1, wherein, if the leakage current flowing throughsaid discharge load before the start of the discharge is denoted It(A),the stationary discharge voltage is denoted E(V), and the frequency ofthe alternating current voltage output by said inverter circuit isdenoted F(Hz), then the capacitance C(F) of said trigger capacitor isC>It/(E×F), and the capacitance C(F) is equal to or less than thecapacitance at which full-wave rectification is carried out when saiddischarge load is in the stationary discharge state.
 6. A dischargepower supply apparatus according to claim 2, wherein, if the leakagecurrent flowing through said discharge load before the start of thedischarge is denoted It(A), the stationary discharge voltage is denotedE(V), and the frequency of the alternating current voltage output bysaid inverter circuit is denoted F(Hz), then the capacitance C(F) ofsaid trigger capacitor is C>It/(2×E×F), and the capacitance C(F) isequal to or less than the capacitance at which full-wave rectificationis carried out when said discharge load is in the stationary dischargestate.
 7. A discharge power supply apparatus according to claim 1,wherein capacitors are respectively connected in parallel to all of thediodes in said rectifier circuit, and one of the capacitors is a triggercapacitor that has an electrostatic capacitance that is substantiallylarger than that of the other capacitors.
 8. A discharge power supplyapparatus according to claim 1, wherein the diodes of said rectifiercircuit comprise a plurality of diodes connected serially, capacitorsare respectively connected in parallel to the plurality of seriallyconnected diodes, and a portion of the capacitors among these capacitorsare trigger capacitors having a capacitance substantially larger thanthe other capacitors.
 9. A discharge power supply apparatus according toclaim 7, wherein, if the leakage current flowing through said dischargeload before the start of the discharge is denoted It(A), the stationarydischarge voltage is denoted E(V), and the frequency of the alternatingcurrent voltage output by said inverter circuit is denoted F(Hz), thenthe capacitance of said trigger capacitor is greater than thecapacitance of the other capacitors by It/(E×F) or more, and is equal toor less than the capacity that carries out a full-wave rectificationwhen said discharge load is in the stationary discharge state.
 10. Adischarge power supply apparatus according to claim 3, wherein saidinverter circuit is a multi-phase inverter, said transformer is amulti-phase transformer having a plurality of primary windings andsecondary windings, and said rectifier circuit is a multi-phaserectifier circuit having a plurality of diode arms.
 11. A dischargepower supply apparatus for supplying a direct current voltage to adischarge load and discharging the same, comprising: an inverter circuitthat converts direct current voltage to alternating current voltage; afull-wave rectifier circuit that rectifies an alternating currentvoltage generated by said inverter circuit; a trigger capacitor and atrigger diode is connected in series between the input side and theoutput side of said full-wave rectifier circuit; and a charging diodeconnected between the input side of said full-wave rectifier circuit andthe junction of said trigger capacitor and said trigger diode, wherein,at the start of the discharge, the voltage of said trigger capacitor issuperimposed on the voltage of said secondary winding to supply to thedischarge load a trigger voltage that is higher than the stationaryoutput voltage, and after the start of the stationary discharge, adirect current power output from said full-wave rectifier circuit issupplied to said discharge source.
 12. A discharge power supplyapparatus according to claim 11, wherein a smoothing capacitor or asmoothing capacitor and a bypass diode are provided at the output ofsaid full-wave rectifier circuit, and the cathode of said trigger diodeand the cathode of said bypass diode are connected.
 13. A dischargepower supply apparatus according to claim 11, further comprising atransformer having a primary winding, to which the alternating currentvoltage output by said inverter circuit is applied, and a secondarywinding.
 14. A discharge power supply apparatus according to claim 13,wherein said transformer has two connected serially secondary windings,said full-wave rectifier circuit is a center tap rectifier circuitcomprising a pair of diodes connected serially to each of the terminalsof said two secondary windings, and said charging diode is connectedbetween the junction of said two connected serially secondary windingsand the junction of said trigger capacitor and said trigger diode.
 15. Adischarge power supply apparatus according to claim 13, wherein saidtransformer has two connected serially secondary windings, saidfull-wave rectifier circuit is a center tap rectifier circuit comprisinga pair of diodes connected serially to each of the terminals of said twosecondary windings, and said charging diode is connected between theother terminal of said two connected serially secondary windings and thejunction between said trigger capacitor and said trigger diode.
 16. Adischarge power supply apparatus according to claim 11, wherein thecapacitance C(F) of said capacitors has values that satisfy the formula:C>It/(F×E) where It(A) denotes the discharge current before the start ofthe discharge, E(V) denotes the discharge voltage of the stationarydischarge state, and F(Hz) denotes the converted frequency of theinverter circuit, and the capacitance C(F) is equal to or less than thecapacity for carrying out full-wave rectification when said dischargeload is in the stationary discharge state.